1. Field of the Invention
The present invention relates generally to an apparatus and method for emphasizing an edge in an image, and more particularly, to an image generating apparatus and method for emphasizing an edge in an image based on image characteristics, such as brightness variation, or contrast in the image, complexity, and so forth.
2. Description of the Related Art
Generally, edge region detection of an image is accomplished with an edge-detecting filter, alone or in combination with a noise canceling scheme.
Edge region detection using the edge detecting filter extracts an edge region by using an edge extracting filter such as a Sobel operator, a Canny edge detector, Laplacian filter or Laplacian of Gaussian filter, or the like, emphasizes the edge region by applying an edge gain to the extracted edge region, and applies the emphasized edge region to the original image, thus generating an edge-emphasized image. This method is one of several widely used methods to detect an edge region in a low-pass-filtered original image.
The edge region detection using both the edge detecting filter and the noise cancelling scheme extracts a high frequency of the original image by using a band pass filter, whereby noise is also extracted together with the edge region. Since this method also amplifies noise when applying the edge gain to the extracted edge region, it cancels the noise by using a Laplacian of Gaussian filter.
Alternatively, with a separately provided noise cancelling filter, noise may be previously cancelled prior to detection of the edge region in the original image. A thresholding scheme may also be used in which the edge region is detected in the original image and an edge value smaller than a predetermined threshold is removed such that the edge region can have only large edge values.
As such, an edge region is conventionally emphasized by using the edge detecting filter or both the edge detecting filter and the noise cancelling scheme.
However, when an edge is emphasized using the conventional methods, it is difficult to increase an edge gain due to accompanying amplification of noise in the original image and to cancel the noise suitably for respective regions of the original image having different image characteristics.
Moreover, in the original image, in case of a dark region having a small difference between the maximum brightness and the minimum brightness and a bright region having a large difference between the maximum brightness and the minimum brightness, if the edge gain is adjusted based on the bright region, an edge in the dark region is emphasized less than an edge in the bright region.
Furthermore, because there is usually more noise in the bright region than in the dark region, noise cancellation without consideration of brightness may excessively cancel the small noise in the dark region.